Halfspace control system for electronic typewriter with correction register

Abstract

An electronic typewriter comprising keys 12a and an electronic control system 26 for causing a print wheel 16 to print corresponding characters at successive horizontal positions. A register 86B stores and continuously updates its storage of the last plurality of characters printed. When an error is made, the typist can backspace to the error, automatically recall the incorrect character from the register and erase it by restriking that character via a correction ribbon 28. Actuating a halfspace mode key 24 advances the print wheel's horizontal position by one-half the ordinary space, thereby moving out of normal registration to permit inserting extra characters. Upon such actuation of the halfspace key, the register's contents are cleared so that characters entered in normal registration cannot be used while the print wheel is in an offset location. Characters typed while in halfspace mode are stored in the usual manner. When return to normal registration is desired, the halfspace key is released, again advancing the print wheel's horizontal position by one-half space. Upon such return, the register's contents are again cleared to preclude any non-correspondence between the position of characters taken from the correction register and current registration of the print wheel.

What is claimed is: 
     
       1. A halfspace control system for a typewriter comprising a keyboard containing character keys; an electronic system responsive to electrical outputs from said keyboard for generating control signals; mechanical striking means capable of striking any of the characters from said keyboard against a platen and moving across said platen, said mechanical striking means being responsive to said control signals for striking selected characters, corresponding to those selected upon operation of said keyboard, against said platen and moving a predetermined distance in a predetermined direction across said platen upon the striking of each character against said platen; storage means within said electronic system for storing and continuously updating its storage of the last plurality of characters struck against said platen; backspace and correction means within said electronic system for selectively causing said striking means to move in discrete steps, each step being of said predetermined distance, in a direction opposite to said predetermined direction and for selectively restriking the characters stored in said storage means in registration with the respective positions previously struck against said platen; a halfspace manually controllable input means within said typewriter; and halfspace control means within said electronic system responsive to a first operation of said halfspace input means for (A) causing said mechanical striking means to move across said platen by one-half said predetermined distance and (B) erasing the contents of said storage means in conjunction with execution of said half-distance motion of said striking means across said platen. 
     
     
       2. The typewriter of claim 1 wherein said mechanical striking means comprises a movable printing element containing all the characters of said keyboard at different positions on said striking means and a movable carrier for said printing element for moving said printing element in said predetermined direction or the reverse of said predetermined direction across said platen, said backspace and correction means being arranged selectively to move said carrier in said reverse direction in said discrete steps and to move said printing element into its respective position in accordance with the characters previously struck against said platen, and in accordance with the characters in said storage means, for each respective step of said carrier, up to the number of the plurality of characters stored in said storage means. 
     
     
       3. The typewriter of claim 1 wherein said storage means also stores and continuously updates its storage of the last plurality of characters struck against said platen after its contents have been erased and said mechanical striking means has executed said half-distance motion. 
     
     
       4. The typewriter of claim 3 wherein said halfspace input means is arranged to provide first and second operations and said halfspace control means within said electronic system is also responsive to the second operation of said halfspace input means for (A) causing said mechanical striking means again to move across said platen by one-half said predetermined distance, and (B) erasing the contents of said storage means in conjunction with execution of said second half distance motion of said striking means across said platen. 
     
     
       5. The typewriter of claim 4 wherein said halfspace input means is a switch on said keyboard, the first operation of said halfspace input means being a movement of said switch from a first position to a second position and a resultant change in electrical output to said electronic system from a first condition to a second condition, the second operation of said halfspace input means being a movement of said switch back to said first position and a resultant change in said electrical output to said electronic system back to said first condition. 
     
     
       6. The typewriter of claim 5 wherein said switch is a momentary contact type switch and comprises a key on said keyboard, said first position of said switch being a raised position and said second position of said switch being a depressed position.